Longitudinal relationships among visual acuity, daily functional status, and mortality: the Salisbury Eye Evaluation Study.

IMPORTANCE: Determination of the mechanisms by which visual loss increases mortality risk is important for developing interventional strategies.
OBJECTIVE: To evaluate the direct and indirect effects of loss of visual acuity (VA) on mortality risk through functional status changes among aging adults. DESIGN, SETTING, AND PARTICIPANTS: Prospective longitudinal study of a population-based sample of 2520 noninstitutionalized adults aged 65 to 84 years from September 16, 1993, through July 26, 2003, in the greater Salisbury area of Maryland. Participants underwent reassessment 2, 6, and 8 years after baseline. Mortality status was ascertained from linkage with the National Death Index through 2009. EXPOSURES: Results of VA testing and self-reported functional status based on activities of daily living (ADL) and instrumental ADL (IADL). MAIN OUTCOMES AND MEASURE: Mortality.
RESULTS: Worse VA levels at baseline were associated with an increased the risk for mortality (hazard ratio [HR], 1.16 [95% CI, 1.04-1.28]; P < .01) through their effect on lower IADL levels at baseline. Declines in VA over time were associated with increased mortality risk (HR, 1.78 [95% CI, 1.27-2.51]; P < .001) by way of decreasing IADL levels over time. Participants experiencing the mean linear decline in VA of 1 letter on the Early Treatment Diabetic Retinopathy Study acuity chart per year are expected to have a 16% increase in mortality risk during the 8-year study exclusively through associated declines in IADL levels. CONCLUSIONS AND RELEVANCE: In this longitudinal study of older adults, VA loss adversely affected IADL levels, which subsequently increased the risk for mortality. Prevention of disabling ocular conditions, treatment of correctable visual impairment, and interventions designed to prevent the effect of visual impairment on IADL declines may all reduce mortality risk in aging adults.